OK. I've been doing searches and reading through these threads for several days and can't figure what the next step would be. A friend of a friend has an 05 Roadster that won't crank. He replaced the RCM, checked fuses, connectors and harnesses. I'm not sure what else. When I heard about the problem I said "It's the RCM'. I brought my 05 Coupe to his shop and had him pull my RCM (since we know it works) and put it in the no start car. It cranked like 1/2 a crank and then nothing. We put his RCM in my car and my car started fine. So we though, might be the PCM then. Same thing. We put my PCM in his car, it cranked 1/2 a crank and then nothing. Put his PCM in my car and it starts fine. So, at this point we know his RCM and PCM are good since they both worked fine in my car. The battery and starter both test good as well. Any ideas on what to look at from here?

 

Are there any codes? Have you checked the grounds for corrosion or being loose? Have you examined the RCM connectors for any traces of burning or corrosion? When you turn the key to the On position, do all the dash lights light up. Does the black rectangle in the instrument cluster change to a D? Does the fuel pump start for a few seconds after the key is in the ON position. Do the door locks work (this checks if the CLP/SS is working)? Does the key fob open and close the door locks (checks the SKREEM receiver) ? Has it rained lately, and have you noticed any wetness on the passenger's side carpet (the TMU is under the passenger carpet). Did you spill anything on the shifter (if the ECU doesn't know what gear you're in, won't crank)?
With a little more info, should be able to narrow it down.
Good Luck, keep us updated.
-Jerry

 

Thanks Jerry. I'm just going to print this out and give it to him as I have no idea what the answers are to any of that (except, no codes). My involvement thus far was pretty much just what I posted. I appreciate your input! I'll keep you posted!

 

For the hell of it replace fuse # 11 in the engine bay fuse box near the brake master cylinder. That's the one for the ignition. Maybe it's crapping out.
Also unscrew the coils and check the backs for cracks in them. Maybe one is grounding out when you try to start it. Check the spark plug wires also, as one of them could be grounding out.
Good luck!

 

Could possibly be the Skreem module. If you disconnect and reconnect the battery does it try and do the "1/2 cranks" and then nothing? Research Skreem module on the forum and see if the symptoms don't mimic a bad Skreem.

 

I would have the battery "TESTED" and clean all connections at both ends. The battery wires have also been known to corrode on the inside.

 

Check your wiring harness at the bottom of both boxes under the hood. I had mice get into one and I had to replace some of the wires. And sometimes if your key is wobbly in its flip case the car want read it. Or it'll unlock the cylinder but not send the signal to everything thats required to start the car. I've ran into some out there stuff with these cars.

 

Any updates on this? I am having the same problem. Replaced the RCM about 6 years ago and barely drive the car. I go to start it last weekend and I get a click. Threw a jumper on it and starts right up. Took the jumper cable off and turn the car off but it won't start back up. The auto store tested the battery and said it was fine but gave me a new battery anyway. Plug it in and first attempt won't start. Second attempt started right up. Every time after it starts right up. I just want to figure this out so I don't get stuck somewhere. I am wondering if the starter is starting to act up.

 

Have you checked all of the cable connections, both ends? Sometimes it doesn't hurt to clean them even if you don't see corrosion.

 

Hi!

I have been looking for the broblem "Car died 07.05.2025" totally.

Canbus was missing, no crank no start nothing.

AND no help anywhere !!!

Last thursday found a gay having Xentra-tester and a lot of expirience of died MB:s.

Unfortenately summer is gone, just hoping next week 1 sunny warm day.

Today he called: PCM has lost it's memory !!!!! And he knows how to fix it.